Dual-channel ratiometric sensing of hypochlorous acid based on organic cage with red and green fluorescence

The high-performance detection of hypochlorous acid (HClO) is crucial for life and environmental health, but still challenging for the single fluorescence signal and single sensing channel of probes. Organic cage with strong adsorption ability and cage structure-related fluorescence property, is a type of potential fluorescent probe. However, the single signal and short emission of organic cage hinders its sensing performance. The design of dual emitting organic cage with long wavelength for dual-channel ratiometric sensing of HClO is of great significance. Herein, we reported an organic cage (ROX) as a probe for accurate quantification of HClO. The prepared ROX exhibited capsule topology-facilitated red/green dual emission around 660/502 nm. The cage-like structure was disrupted by the rapid specific redox interaction between imine bond in ROX and HClO. As a result, the fluorescence at 660 nm quenched in conjunction with the enhancement at 502 nm in PBS (pH 4). Besides, the fluorescence increased at 582 nm with constant emission at 480 nm in DMSO/PBS (pH 7) (V/V, 9/1). The ratio signal in PBS and DMSO/PBS respectively gave the linearity range of 1-30 and 20-45 μM, the limit of detection (3 s) of 14 and 49 nM, and the relative standard deviation of 1.04 % and 0.54 % for 10 replicate determinations. Based on the mutual validation of dual ratio, the dual-channel ratiometric sensing possesses good accuracy, sensitivity, selectivity, and precision. Moreover, ROX can be applied to HClO monitoring in actual water and disinfectant samples with the recoveries of spiked HClO ranged from 95.0 % to 104.2 %. The proposed sensing method highlights the great potential of organic cage in fluorescence sensing.